1. Field of the Invention
The present invention relates to a material for inverting positive static electricity (hereinafter referred also to as "static electricity inverting material") and to a method for removing static electricity. The invention also relates to a crop rasing house used for keeping warm or sheltering crops from outside, and to a method for raising crops with the use of the crop raising house.
2. Description of Related Art
While there are cases where the static electricity is used advantageously, the static electricity may sometimes lead to the following harmful effects. Namely, when the static electricity is generated, there arise dynamic troubles such as adhesion or tangling of electrically charged material such as powders, fibers, sheets and the like to another material. Furthermore, in some cases, a combustible substance or an explosive substance takes fire or explodes when the static electricity is discharged. When a human body is charged with electricity, he or she receives electric shocks when discharging the electricity through contact with a grounded conductor. Moreover, the static electricity may be a cause for break, erroneous operation, or deterioration of quality in precision devices including semiconductor parts.
It has been said that the positive static electricity affects human bodies, causing kinds of diseases and troubles in health. In a positive electrostatic environment, the amount of cations existing in the air is high, so that the amount of cations in a human body increases correspondingly. As a result, the human body fails to actively undergo metabolic change thereby to decrease resistances to disease to be frequently taken ill. For instance, cations induce shoulder stiffness or sleep. On the other hand, anions favorably influence and activate cells, blood or moisture in human bodies (living bodies). The foregoing is well-known, and in this connection the presence or appearance of the positive static electricity is supposed to represent the decrease of anions.
For example, the interior of a running automobile is charged with positive electricity (700 to 1000 V) due to the friction of the automobile body with the air, whereby the driver becomes sleepy. That is, the static electricity is prone to cause car accidents. Not only automobiles, but also a variety of living environments produce the static electricity. Most of the articles including fluids produce static electricity, by way of familiar examples, image forming apparatuses using electron beams (TV sets, display devices and the like), fluorescent lamps, electric appliances such as air conditioners wherein liquid or gas flows, and devices using fluids such as petroleum, gas or the like (heaters and the like). Human bodies are exposed to the static electricity via these household appliances in considerably frequent occasions.
In the meantime, the potential in the air varies depending upon conditions of the weather and ground surface. For example, when a cold front or low atmospheric pressure passes, cations increase on the ground surface. Moreover, the concentration of cations is high also where an inverse wind or reverse wind rises easily. When cations increase, plants are hindered from growing well or badly damaged by diseases and pest insects. Meanwhile, when there is a columnar object standing straight on the ground surface, a slantwise potential difference increases in a space of a conical shape extending from the peak to the ground surface, so that a potential gradient is formed. In this conical space, the concentration of anions is high and therefore plants grow predominantly.
Among the factors influencing anion and cation concentrations other than the above, one is static electricity. In general, the cationic concentration is high in a positive electrostatic atmosphere, while the anionic concentration is high in a negative electrostatic atmosphere. In the case where about (+) 0.2 to 0.3 kV of static electricity exists in the atmosphere, it is possible to favorably raise crops if the static electricity is removed or turned into negative one. Particularly, when a vinyl house is used for raising crops, the external wind generates friction to the vinyl sheet, resulting in the increase of positive static electricity in the internal space. Besides, when the house is equipped with a ventilating means or air conditioning equipment, the stream of air is brought about inside the house, so that the positive static electricity is furthermore increased.
In order to eliminate such static electricity, there are a method whereby the electric charges are released quickly by increasing the conductivity of an object (e.g., by connecting the object to an earth line one end of which is buried in the ground), a method whereby ions having a different polarity are supplied to the generated electric charges by means of a discharging device utilizing an isotope or AC corona discharge thereby to neutralize the electric charges, a method of discharging the electricity in the air, etc.
It is, however, difficult to completely remove the static electricity in these methods, and it is needless to say that a large-scaled apparatus is required to turn the positive static electricity into negative.